The present invention relates in general to police radar detectors and, more particularly, to a novel input stage for a police radar detector which input stage efficiently interconnects an antenna, a local oscillator, a mixer and an intermediate frequency amplifier within the input stage.
Police have used radar waves to monitor the speed of motor vehicles for many years. The frequencies currently licensed in the United States for police radar waves include: the X band--10.50 gigahertz (Ghz) to 10.55 Ghz; the K band--24.05 Ghz to 24.25 Ghz; and, the K.sub.a band--33.40 Ghz to 36.00 Ghz. To alert motorists of the presence of police radar, electromagnetic signals within these police radar bands are monitored using a police radar detector which issues an audible and/or visual alert upon detection of a radar signal within one of bands.
Police radar detectors are basically superheterodyne radio receivers in which the tuning of the receivers is repeatedly swept through the frequencies which are to be received or detected, i.e., the frequencies of the licensed police radar bands. A typical superheterodyne radio receiver includes a mixer for receiving electromagnetic signals and a local oscillator (LO) signal to convert the frequency of the received signals to the frequency of an intermediate (IF) amplifier with the LO being swept in frequency to tune the required frequencies. Incoming electromagnetic signals can then be received at the LO frequency plus or minus the IF frequency.
It is important to process received electromagnetic energy as efficiently as possible within a police radar detector so that weak radar signals can be effectively detected. An operator of the detector can then be alerted of the presence of police radar signals at the earliest possible time giving the operator sufficient advance notice that the operator can verify that he or she is operating their vehicle at an appropriate speed. To this end, input stages for police radar detectors must efficiently interconnect an antenna, the LO, the mixer and the IF amplifier so that there is minimal loss of each signal from the signal's source to its destination.
In the interest of advancing the art and to provide improved performance for police radar detectors, there is an ongoing need for novel and improved arrangements for input stages for police radar detectors.